I have an outdoor shed thats sort of a hang out for me and my friends. I had a cigar box full of coins stored in it for a long time (winter). Now its July, I pulled out the cigar box and all the coins (nickels and quarters) have turned the color of pennies. What happened? Did they rust? Did they absorb the color of the pennies?

At 7/25/2011 12:32:10 PM, Rockylightning wrote:I have an outdoor shed thats sort of a hang out for me and my friends. I had a cigar box full of coins stored in it for a long time (winter). Now its July, I pulled out the cigar box and all the coins (nickels and quarters) have turned the color of pennies. What happened? Did they rust? Did they absorb the color of the pennies?

What years are they and where do you live?

Most likely, there was a chemical reaction with the climate and they probably oxidized. But, if we get the year of some of them, we can find out what chemical they are made of, to see what common chemcial reactions they can go through (then compare that list of common reactions to the known environment).

I'm going to guess that the cigar box is a wooden box, likely a thin light wood. These woods (much like using oak for wine and whiskey barrels) are designed to allow air to pass through them. If this was recently used for cigars, it is likely that some of the chemicals in the cigars passed into the wood where they stayed (does the wood still smell like cigars?). These chemicals likely have sulfide (or there may be another source of sulfide) that would react to both the copper and nickel in the coins.

A fun experiment would be to place some coins in the cigar box, as well as some in an air tight bag in the cigar box. Also, place some coins in a metal box (both some in a bag, and some not), and place some coins just on a shelf (some open, some in a bag).

It is likely that the chemicals could have come from anywhere in the shed. Perhaps if you use pesticides, and store the chemicals in the shed. There are just so many things that could cause this in a shed.

At 7/25/2011 9:37:44 PM, Rockylightning wrote:The cigar box hasnt seen cigars for at least 5 years (though it still smells like it. Mmmm). I will note that the dimes (all of them) are unaffected.

That causes a question, since dimes are made out of the same material as both quarters and nickels (75% Cu, 25% Ni cover, with a Cu core). Since they are the same chemical, it does not make sense that only some coins would be affected (all the nickels and quarters, but no dimes).

Now, none of the dimes are annual collectors (made from 90% silver), right? Or pre-1965 (when they changed from silver to the current make-up)?

It's going to be hard to say over the internet, but it would be interesting (at least I would find it interesting) to take them to the High School Chemistry teacher to see if you (maybe as a class project or something) can find a way to test the coins and find out what is going on (we did a little of that in my AP Chem class years ago, though not on coins).

Hmm.. This is very strange. Some of the coins (the dimes and nickels) are only affected on one side of the coin. Also, after re examining the box, I noticed the outlines of the coins printed into the wood, the outlines are made of what looks like battery acid (the same substance is also found on the pennies).

At 7/26/2011 10:01:21 PM, Rockylightning wrote:Hmm.. This is very strange. Some of the coins (the dimes and nickels) are only affected on one side of the coin. Also, after re examining the box, I noticed the outlines of the coins printed into the wood, the outlines are made of what looks like battery acid (the same substance is also found on the pennies).

I'm going to run some experiments.

Is the ring a light white powder that can be scrubbed away with moderate elbow grease (meaning not in a single swipe, but doesn't take more than 60 seconds to wipe away).

At 7/26/2011 10:01:21 PM, Rockylightning wrote:Hmm.. This is very strange. Some of the coins (the dimes and nickels) are only affected on one side of the coin. Also, after re examining the box, I noticed the outlines of the coins printed into the wood, the outlines are made of what looks like battery acid (the same substance is also found on the pennies).

I'm going to run some experiments.

Is the ring a light white powder that can be scrubbed away with moderate elbow grease (meaning not in a single swipe, but doesn't take more than 60 seconds to wipe away).

Typically, the copper in the coins will naturally form copper oxide with the air (making them dull looking and greenish), however, that requires open air (while a wooden box is not the best vacuum seal, it is still somewhat of a barrier to nature. Also, the imprints that were left seem to imply that there was more chemical reaction than just the oxidation of copper.

You see to have a thin oxide toning. It could be air pollution, but I'm inclined to blame the cigar box for out-gassing something that works with moisture from the air, assuming the box is cardboard rather than cedar. Actually, maybe cedar does something too.

You might try putting a handful of coins into a sock, tying the sock closed, and running it through the clothes washer. Any coin with collector value should never be cleaned in any way. Leave them toned.

There is a hotel in San Francisco, the St. Francis, that has a tradition of only using shiny coins. they have a guy who cleans coins for a living. I recall the procedure involves soaking with toilet bowl cleaner. A web search would find the method.

It was stated that these are all 2003 coins so there isn't going to be collector value in them, however, a vinegar and salt mixture is ideal for removing Cu(I) and Cu(II) (copper oxides).

My guess is that the white powder is Copper Sulfate. This comes when sulfuric acid reacts with oxidized copper (sulfur came from the tobacco products). When it happens in a dry place (the wood will absorb the water in the air as it passes through the wood), it forms a white powder.

If you add the white powder to water, it should turn the water blue (don't add it to too much water), and if you let the water evaporate, you'll be left with a cool blue crystal (if you boil the water, you will lose most the blue).

The reason for the blue coming or going is because when dissolved in water, it picks up water atoms (up to 5). These water atoms make it blue, but as you heat the copper sulfate, it looses water atoms (loses 2 of the 5 at 63 C, and another 2 at 109 C). So if you boil the water, you'll heat it up so that you loose 4 of your 5 water atoms (and so most of the blue).

Also, upon dissolving the CuSO4 into the water, it should warm the water a bit (again, if you use too much water, you'll never tell the increase).

If you use distilled water, you can just add a bunch of water and then let it evaporate over time, and it should then leave a blue powder (since it is distilled, there will be nothing else in the water).

The reason for the blue coming or going is because when dissolved in water, it picks up water atoms (up to 5). These water atoms make it blue, but as you heat the copper sulfate, it looses water atoms (loses 2 of the 5 at 63 C, and another 2 at 109 C). So if you boil the water, you'll heat it up so that you loose 4 of your 5 water atoms (and so most of the blue).

Also, upon dissolving the CuSO4 into the water, it should warm the water a bit (again, if you use too much water, you'll never tell the increase).

If you use distilled water, you can just add a bunch of water and then let it evaporate over time, and it should then leave a blue powder (since it is distilled, there will be nothing else in the water).

Of course, this is just a guess.

I didn't know you had it in you Ore_Ele. I wish I was sciency like you... *adoring sigh*